1. Technical Field
This disclosure relates to receiver synchronization techniques based on preamble structure of physical layer frames.
2. Related Art
The first version of the 802.11 wireless communication standard was ratified only 14 years ago, in 1997. While initial adoption of that technology was slow, today there is almost no end to the spectrum of electronic devices that incorporates wireless communication technologies (e.g., cell phones, global positioning system (GPS) devices, and laptop computers), nearly no end to the environments in which wireless communication devices are used (e.g., in the home and automobile), and nearly no end to the services consumed by wireless communication devices (e.g., streaming music and High Definition (HD) television). Consumer and business demand for wireless communication have driven, and continue to drive, significant advancements in wireless communication.
Advancements in data rate provide an example. The 802.11 standard rapidly evolved from originally providing only 1.2 Mbps throughput, to 11 Mbps under 802.11b, to 54 Mpbs under 802.11g, to 600 Mpbs under 802.11n. At the same time, audio and video technology have evolved, and the massive amounts of data needed to provide HD video (e.g., 1920×1080 video) and other services now drive a further need for improved wireless data rate and capacity. Partially in response to this need, version 1.0 of the 60 GHz Wireless Gigabit Alliance (WiGig) specification provides data transmission rates of up to 7 Gbps, which is more than 10 times faster than the highest data rate that the 802.11n standard supports.
However, no wireless device can take advantage of the extensive array of wireless services now available, without first having the ability to acquire the transmitted signal. There are so many impairments that can affect the wireless waveform that the transmitted signal must be carefully designed (e.g., to include synchronization and channel estimation preambles), and even more carefully processed upon reception, to provide the receiving device with some realistic opportunity to successfully recover any data. These impairments include, as examples, multipath interference, frequency offsets, power fades, imperfections in the receiver front end (e.g., imperfections in the receive antenna, demodulator, analog to digital converters, mixers, and other front end logic).
For these reasons and others, acquiring the transmitted signal is not a trivial matter. Further improvements in signal acquisition are needed, particularly with regard to acquiring weak power signals. Being able to acquire weaker signals also increases the opportunities for recovering data over longer distances.